In semiconductor integrated circuits, inductors and transformers are key components commonly used by designers and manufactures. For instance, the inductors are utilized for the purpose of widening the frequency band and/or of matching the impedance. Generally, the inductor for a semiconductor integrated circuit has a spiral-like conductive line formed on a plane. The impendence of the inductor depends upon the turning number and the occupied area of the spiral-like conductive line. The impendences of inductors are easily affected by some causes such as process variation and packaging structures, and therefore the actual impendences of inductors probably depart from the design values.